Method and apparatus for improving the tensile strength of a multifilament glass strand

ABSTRACT

An apparatus and method for improving the tensile strength of a resin impregnated multifilament glass strand are disclosed. The glass strand is conveyed through an impregnating solution, simultaneously being maintained under tension while being vibrated. Each filament vibrates at its respective, natural frequency with the result that the glass strand separates into its component filaments thereby exposing a plurality of interstices to the solution so as to increase the amount of solution absorbed, whereby the tensile strength of the resin impregnated glass strand is improved.

iEQ orsch States Patent [1 1 METHOD AND APPARATUS FOR KMPROVHNG THE TENSELE STRENGTH OF A MULTKFILAMENT GLASS STRAND [75] Inventor: Robert E. Dorsch, South Bend, Ind. [73] Assignee: Uniroyal, 11nc., New York, NY. [22] Filed: Dec. 10, 1971 [21] App]. No.: 206,770

2,715,079 8/1955 Rhodes, Jr. 117/102 2,694,307 11/1954 Henry 68/43 3,413,186 11/1968 Marzocchi 161/176 Primary ExaminerDanie1 J. Fritsch Attorney-Robert .1. Patterson 57] ABSTRACT An apparatus and method for improving the tensile strength of a resin impregnated multifilament glass strand are disclosed. The glass strand is conveyed through an impregnating solution, simultaneously being maintained under tension while being vibrated. Each filament vibrates at its respective, natural frequency with the result that the glass strand separates into its component filaments thereby exposing a plurality of interstices t0 the solution so as to increase the amount of solution absorbed, whereby the tensile [56] Referen e Cited strength of therresin impregnated glass strand is im- UNITED STATES PATENTS proved 2,775,860 l/1957 Morrison 156/180 12 (Ilaims, 3 Drawing Figures 7 L .DfYl/YG 3 M t 1 1 I) en W --Z0 -z 13 Z 5 METHOD AND APPARATUS FOR IMPROVING THE TENSILE STRENGTH OF A MULTIFILAMENT GLASS STRAND BACKGROUND OFTHE INVENTION This invention relates to apparatus and method for making an impregnated multifilament glass strand, and, more particularly, a glass strand which has had its tensile strength improved by increasing the amount of adhesive solution absorbed between the filaments of the glass strand.

In the manufacture of many artificial textile fibers, it is frequently required to impregnate freshly spun filamentary products with a solution in order to provide them in a satisfactorily useful and commercially acceptable form. For the purpose of impregnating and otherwise processing many synthetic and artificial textile fiber materials subsequent to spinning, it is usually convenient and expedient to form continuous or endless filamentary lengths. These filamentary' lengths are assembled in multiple filament bundles in which a plurality of individual, component continuous filaments are handled in a closely associated substantially parallel relationship. i

The most common method of impregnating these fil-' aments is merely todip the material within a fluid bath containing the impregnating solution as in C. F. Oldershaw, US. Pat. No. 3,074,775 issued Jan. 22, 1963. Each dip of the material may be followed by a passage of the material between squeezing rollers. However, with many textile materials such as those having multifilaments, the mere dipping of the material within the solution and subsequent squeezing is not sufficient to produce an even and thorough penetration of the impregnating solution between all the filaments of the material. I

An alternate method which has heretofore been utilized to produce a more uniform diffusion and penetration of the impregnating solution is to convey the multifilament material through a bath by means of rollers and at the same time to vibrate or agitate the material while it is within the bath. Such typical devices alternately stretch and relax the filaments of the material in order to increase the penetration of .the impregnation solution as may be seen in the US. Pats. to G. E. Henry Pat. No. 2,694,307 issued Nov. 16, 1954; G. Campolunghi Pat. No. 2,133,535 issued Oct. 18 1938; and W. T. Harris Pat. No. 2,949,384 issued Aug. l6, I960. Heretofore no means was provided for maintaining each filament in continuous tension as it was being conveyed through the impregnation solution. Conventionally, the multifilament material vibrated as a single entity rather than each of the filaments vibrating at its respective, natural frequency; and in most vibratory apparatus, acoustical means were employed to excite the material rather than the mechanical means of the present system.

Accordingly, it is a primary object of the present invention to provide a method of impregnating a multifilament glass strand so as to overcome the aforementioned disadvantages. I

Another object of this invention isto improve the tensile strength of a multifilament glass strand by increasing the amount of adhesive impregnating solution absorbed between the filaments of the multifilament glass strand.

Another object of this invention is to increase the amount of impregnating solution absorbed by a multifilament glass strand by mechanically vibrating the glass strand as it passes through the impregnating solution.

A further object of this invention is to vibrate a multifilament glass strand as it passes through an impregnating solution in such a way that each filament will vibrate at its respective, natural frequency.

Further objects and advantages of this invention will become apparent and will be better understood with reference to the detailed description and drawings in which:

FIG. I is a schematic view of the apparatus of the invention;

FIG. 2 is a cross-sectional view of a typical multifilament glass strand bundle shown in FIG. 1; and

FIG. 3 is a graph illustrating the relative tensile strength of vibrated multi-filament glass strand as compared with non-vibrated glass strand.

SUMMARY OF THE INVENTION Briefly stated and in accordance with one embodiment of this invention, there is provided a housing for containing an adhesive impregnating solution, means for conveying a multifilament glass strand through the impregnating solution, means for maintaining each filament of the glass strandunder tension as it passes I through the impregnating solution and means for mechanically vibrating the glass strand as it is maintained under constant tension.

A disturbance produced at one end of a glass strand as in mechanical vibration sends a wave or train of waves along the strand to be reflected back and forth from end to end.

When traveling in one direction the wave is on top and upon reflection it flips to the underside being always on top when moving to the right and on the bottom when moving to the left. This gives rise to a vibrating motion of the strand which is directly proportional to the square root of the individual strand tension and inversely proportional to the square root of the mass per unit length of the strand. Since the filament diameter may vary as much as 66 percent from filament to filament (depending on size used) and since the tension varies across the face of each strand the frequency of individual filaments must vary.

The fundamental frequency of the vibration is equal to the number of times per second the wave arrives at the same end. Therefore the pitch will depend on the velocity of the waves and the distance they have to travel. The wave velocity is also a function of the bath fluid viscosity.

Since the tension varies from filament to filament across a strand, the wave velocity and frequency of each filament within a strand will also vary causing an unbalanced phase relationship. The out of phase condition results in separation of the filaments within the strand, thus allowing penetration of the impregnation fluid.

This method of impregnation substantially increases the amount of adhesive absorbed within the glass strand, thus improving its tensile strength.

Now referring to FIG. I, a schematic view of the apparatus of this invention is shown. A tank 1 contains an adhesive impregnating solution 2, into which a multifilament glass bundle 3 is immersed. The bundle 3 is continuously advanced within the solution 2 by means of rotating rollers 6a, 6b, 6c and 6d. The bundle enters the tank at one end as shown by arrow 18. The bundle advances to rotating roller 6a which swings the strand into the solution where it engages rotating roller 6b as shown. The strand then advances to 'roller 6c which swings the bundle out of the solution and on to rotating roller 611. From here the bundle leaves the tank as shown by arrow 15. The strand is kept under substantially constant tension as it moves between rollers 6b and 60. This may be accomplished by the rollers themselves, or by separate tension producing means. If the rollers are used to provide the tension, then rollers 6c and 6d can be made to rotate at a slightly greater rate than rollers 6a and 6b.

As the bundle 3 moves through the solution 2, after passing roller 6b it is engaged by rod 8 at point 9.

Rod 8 is caused to move by vibrator 7 in a vertical manner as depicted by arrows 17. As the rod vibrates, the filaments of bundle 3 are caused to vibrate at their own natural frequency, causing them to separate as illustrated by arrow 10. In so doing, the impregnating solution 2 is facilitated in its flow between the filaments 5, the combined effect of transverse and axial motion being expended mechanically so as to enhance saturation of the interstices in the bundle. When the bundle leaves the tank 1, the interstices 4 between the filaments 5 have absorbed a greateramount of the adhesive solution 2, as a result of the vibration. FIG. 2 is a cross-sectional view of a glass bundle 3 having filaments 5 and interstices 4 therebetween.

Upon leaving the tank 1, the bundle is dried at drying station 19. This causes the adhesive to set more rapidly, so that it will not get the chance to run out from between the interstices.

The solution 2 is heated from 200 F to 250 F at station prior to immersing the glass strand. This improves the flow characteristics of the solution when it comes in contact with the bundle, and also decreases the reaction or set-up time of the adhesive during the drying cycle.

' FIG. 3 shows a graphic comparison between the tensile strengths of vibratory and non-vibratory glass bundles vibrated at various frequencies measured in cycles per minute.

The tensile strength of a standard bundle size of filaments that receives no vibration is shown by line 12 corresponding to 6.1 lbs/end. The tensile strength is measured in units of lbs/endbecause each bundle is a composite average of many filament fibers. Since all of the bundles in the test were approximately the same size, the measurement in end strength is meaningful.

The lines on FIG. 3 bearing the legends l/16 inch Amplitude of Vibrator and U32 inch Amplitude represent plots measured on glass bundles that were subjected to a vibratory amplitude of 1/16 and H32 of an inch, respectively.

As will be seen, a greater tensile strength was obtained using the higher amplitude of H16 of an inch. This makes sense, since the higher amplitude causes a greater separation of the filaments and a resulting increase in the absorption of adhesive in the bundle.

A maximum tensile strength was obtained in the range of between 2,820 and 2,900 CPM.

For the amplitude of Hi 6 of an inch, a maximum tensile strength of 7.8 lbs/end was reached at a frequency of 2,850 CPM.

For the amplitude of 1/32 of an inch, the tensile strength was 7.0 lbs/end at approximately the same frequency.

The adhesive used for the test was 3212, Uniroyal Inc., Mishawaka Plant, and a 7 to 22 percent increase in tensile strength was observed using the inventive vibratory method. Another adhesive which may also be used is Paracril Rubber Cement.

As will be obvious to those skilled in the art, many different materials, adhesives, amplitudes and frequencies may be used within the scope and purview of this invention. As a result, this discussion, with the attached drawings, is meant to be merely exemplary of the inventive concept. Interpretation of the inventive bounds of this invention should be made with respect to the appended claims.

Having thus described my invention, what I claim and desire to protect by letters Patent is:

l. A method of improving the tensile strength of a multifilament glass strand, having interstices formed -between the filaments, said filaments having different diameters, comprising the steps of:

a advancing said glass strand through a body of an adhesive impregnating solution;

b maintaining said glass strand under substantially constant tension as said glass strand passes through said impregnating solution;

c mechanically vibrating said glass strand as said glass strand passes through said impregnating solution while the entire vibrated portion of said strand is completely submerged in said body such that each of said filaments of said glass strand vibrate separately, each at its respective natural frequency, thereby allowing the impregnating solution to flow into the interstices between said filaments; and

d drying said glass strand after said glass strand has absorbed said impregnating solution within said interstices, so as to form a coherent bundle of filaments having improved tensile strength.

2. A method as recited in claim 1, further comprising the step of: e heating said impregnating solution prior to advancing said glass strand through said impregnating solution.

3. A method as recited in claim 2, wherein said impregnating solution is heated to a temperature ranging from substantially about 200 F. up to but substantially no greater than about 250 F.

4. A method as recited in claim 1, wherein said glass strand is vibrated at a frequency ranging from about 2820 cycles per minute to about 2,900 cycles per minute.

5. A method as recited in claim 4, wherein said glass strand is vibrated at a frequency of about 2,850 cycles per minute.

6. A method as recited in claim I, wherein said glass strand is vibrated at an amplitude ranging from about l/32 of an inch to about l/l6 of an inch.

7. A method as recited in claim 6, wherein said glass strand is vibrated at an amplitude of about l/l6 of an inch.

8. A method as recited in claim 1 wherein the entire vibrated portion of the said strand is supported at two spaced points and wherein vibration of said strand is effected by applying mechanical vibrating means directly thereto at a point intermediate said spaced points and located substantially nearer to the first point of support for the moving strand than to the other point of support.

9. An apparatus for improving the tensile strength of a multifilament glass strand, having interstices formed between the filaments, said filaments having different diameters comprising: i I

a container for holding a body of an adhesive impregnating solution; I I means for advancing said glass strand through said body of impregnating solution; v means for maintaining said glass strand under substantially constant tension as said glass strand is being conveyed through said body of impregnating solution; and means for mechanically imparting vibration to said glass strand as said glass strand is being conveyed through said impregnating solution while the entire vibrated portion of said strand is completely submerged in said body such that each of said filaments of said glass strand vibrate separately; each at its respective natural frequency, thus allowing the adhesive to flow into the interstices of said filament bundle, whereby the tensile strength of said glass strand is improved.

10. An apparatus as recited in claim 9, further comprising means for heating said impregnating solution prior to advancing said glass strand through said impregnating solution.

11. An apparatus as recited in claim 9, further comprising means for drying said glass strand after said glass strand has been conveyed through said impregnating solution.

12. An apparatus as recited in claim 9 including two spaced means for supporting the vibrated portion of said strand as it advances through said body, and wherein said means for mechanically imparting vibra tion to said strand directly engages said strand at a point intermediate said two spaced supporting means and located substantially nearer to the first of said spaced supporting means which first engages said strand than to the other of said spaced supporting means. 

2. A method as recited in claim 1, further comprising the step of: e heating said impregnating solution prior to advancing said glass strand through said impregnating solution.
 3. A method as recited in claim 2, wherein said impregnating solution is heated to a temperature ranging from substantially about 200* F. up to but substantially no greater than about 250* F.
 4. A method as recited in claim 1, wherein said glass strand is vibrated at a frequency ranging from about 2820 cycles per minute to about 2,900 cycles per minute.
 5. A method as recited in claim 4, wherein said glass strand is vibrated at a frequency of about 2,850 cycles per minute.
 6. A method as recited in claim 1, wherein said glass strand is vibrated at an amplitude ranging from about 1/32 of an inch to about 1/16 of an inch.
 7. A method as recited in claim 6, wherein said glass strand is vibrated at an amplitude of about 1/16 of an inch.
 8. A method as recited in claim 1 wherein the entire vibrated portion of the said strand is supported at two spaced points and wherein vibration of said strand is effected by applying mechanical vibrating means directly thereto at a point intermediate said spaced points and located substantially nearer to the first point of support for the moving strand than to the other point of support.
 9. An apparatus for improving the tensile strength of a multifilament glass strand, having interstices formed between the filaments, said filaments having different diameters comprising: a container for holding a body of an adhesive impregnating solution; means for advancing said glass strand through said body of impregnating solution; means for maintaining said glass strand under substantially constant tension as said glass strand is being conveyed through said body of impregnating solution; and means for mechanically imparting vibration to said glass strand as said glass strand is being conveyed through said impregnating solution while the entire vibrated portion of said strand is completely submerged in said body such that each of said filaments of said glass strand vibrate separately, each at its respective natural frequency, thus allowing the adhesive to flow into the interstices of said filament bundle, whereby the tensile strength of said glass strand is improved.
 10. An apparatus as recited in claim 9, further comprising means for heating said impregnating solution prior to advancing said glass strand through said impregnating solution.
 11. An apparatus as recited in claim 9, further comprising means for drying said glass strand after said glass strand has been conveyed through said impregnating solution.
 12. An apparatus as recited in claim 9 including two spaced means for supporting the vibrated portion of said strand as it advances Through said body, and wherein said means for mechanically imparting vibration to said strand directly engages said strand at a point intermediate said two spaced supporting means and located substantially nearer to the first of said spaced supporting means which first engages said strand than to the other of said spaced supporting means. 